Gastrointestinal Defense Mechanisms

1. Gastrointestinal Defense Mechanisms Acidity in the stomach limits the number of viable microbes that gain access the small intestine

3. Gastrointestinal Defense Mechanisms Epithelium serves as a barrier with tight junctions between individual enterocytes forming an epithelial monolayer that prevents the passage of large molecules

4. Gastrointestinal Defense Mechanisms Epithelium serves as a barrier with tight junctions between individual enterocytes forming an epithelial monolayer that prevents the passage of large molecules Enterocytes on villi are replenished every 3 to 6 hours, this minimizes the opportunity for successful colonization by potential pathogens

5. Gastrointestinal Defense Mechanisms “Colonization resistance” is the ability of normal microbes to inhibit the colonization of invading microbes in the intestine

6. Gastrointestinal Defense Mechanisms “Colonization resistance” is the ability of normal microbes to inhibit the colonization of invading microbes in the intestine Inhospitable pH, nutrient competition, competition for attachment sites, local production of antibiotics called “bacteriocins”

7. Gastrointestinal Defense Mechanisms “Colonization resistance” is the ability of normal microbes to inhibit the colonization of invading microbes in the intestine Inhospitable pH, nutrient competition, competition for attachment sites, local production of antibiotics called “bacteriocins” Microhabitat communities are characteristic of a species and to some extent the nutrition and environment of the animal

8. Gastrointestinal Defense Mechanisms Germfree rodents (without normal gut bacteria), all the immunologically important organs (including intestine) are underdeveloped

9. Gastrointestinal Defense Mechanisms Germfree rodents (without normal gut bacteria), all the immunologically important organs (including intestine) are underdeveloped Direct fed microbials enhance immunity and growth in young pigs

10. Mucosal Immunology

11. Mucosal Immunity – Pig Intestine Antibodies in colostrum provide the source of immune protection for newborn pigs

12. Mucosal Immunity – Pig Intestine Antibodies in colostrum provide the source of immune protection for newborn pigs Maximum immunoglobulin absorption occurs 4-12 hours after initial suckling and then declines rapidly due to gut closure

13. Mucosal Immunity – Pig Intestine Antibodies in colostrum provide the source of immune protection for newborn pigs Maximum immunoglobulin absorption occurs 4-12 hours after initial suckling and then declines rapidly due to gut closure During this time, colostrum immunoglobulins are absorbed across the intestinal epithelium and into lymphatic vessels

14. Mucosal Immunity – Pig Intestine Serum antibodies have been detected as early as 3 hours after birth and can be similar to those of the sow within 24 hours after birth.

15. Mucosal Immunity – Pig Intestine Serum antibodies have been detected as early as 3 hours after birth and can be similar to those of the sow within 24 hours after birth. The initial antibody profile acquired via colostrum is restricted to antigens to which the sow has been exposed

16. Mucosal Immunity – Pig Intestine Predominant immunoglobulin in colostrum is IgG and while maternal IgG will protect against systemic pathogens, pathogenic agents are encountered at mucosal surfaces where IgG antibodies are rarely found

17. GUT ASSOCIATED LYMPHOID TISSUE(GALT) One of the major subdivisions of the immune system 25% of intestinal mucosa is lymphoid tissue

18. GALT Major lymphoid compartments: Lymphocytes are present between intestinal epithelial cells lining the intesintal villus Organized lymphoid follicles (Peyers patches) Scattered individual or small aggregates of lymphoid follicles

19. Mucosal uptake of bacteria M cells are found in the epithelium overlaying Peyer’s patches

20. Characteristic features of MALT

21. M cells facilitate antigen uptake.

22. M cells Originate from epithelial cells that are induced to differentiate, contain few lysozomes and low levels of phosphatase

23. M cells Originate from epithelial cells that are induced to differentiate, contain few lysozomes and low levels of phosphatase Serve as a channel for entry of molecules into the underlying mucosal follicular region

24. M cells Originate from epithelial cells that are induced to differentiate, contain few lysozomes and low levels of phosphatase Serve as a channel for entry of molecules into the underlying mucosal follicular region Bacterial binding to M cells may be favored to binding to other epithelial cells, (binding events may be mediated by distinct surface interactions)

25. Mucosal Immunology - Introduction

26. Mucosa-associated lymphoid tissue (MALT)

27. Oral Tolerance

28. ucosal Immunology- Lecture Outline -